| Term | Definition |
| Agglutination | The clumping of red blood cells caused by antibodies binding to antigens on their surface. |
| Alleles | Different versions of a gene that determine traits, such as blood type (A, B, or O). |
| Antibodies | Proteins produced by the immune system that bind to specific antigens to neutralize or mark them for destruction. |
| Antigens | Molecules (often glycoproteins or glycolipids) on cell surfaces that trigger an immune response. |
| Codominant inheritance | A pattern of inheritance where both alleles are fully expressed, such as in Type AB blood. |
| Forward blood typing | A test that identifies antigens on red blood cells using known antibodies (anti-A, anti-B). |
| Glycoproteins or glycolipids | Molecules on the surface of red blood cells that act as antigens and determine blood type. |
| Reverse blood typing | A test that identifies antibodies in plasma using known red blood cells (A or B cells). |
| Rh factor | A protein (antigen) on red blood cells; presence = Rh⁺, absence = Rh⁻. |
| Type A blood | Blood type with A antigens on RBCs and anti-B antibodies in plasma. |
| Type AB blood | Blood type with both A and B antigens on RBCs and no anti-A or anti-B antibodies. |
| Type B blood | Blood type with B antigens on RBCs and anti-A antibodies in plasma. |
| Type O blood | Blood type with no A or B antigens on RBCs and both anti-A and anti-B antibodies in plasma. |